Automated call establishment systems, often referred to as telephone dial systems, are known in the art. These systems are often used to deliver pre-recorded messages or connect call handling agents to telephone subscribers. Typically, such systems automatically dial pre-identified telephone subscribers and present the pre-recorded message or call handling agents to the subscribers once a placed call has been answered.
Call progress analysis techniques are often used to assess if a call has been answered, and if so, if the call has been answered by a human or machine. If the call is answered by a machine, it may be undesirable to connect a call handling agent to the call, instead a specific pre-recorded message might be played or the call may disconnected. Similarly, calls answered by a human may be transferred to an agent, or presented with a different pre-recorded message.
Typically, such techniques rely on call progress tones generated by telephony equipment related to a far end subscriber. Often such call progress tones are unavailable, or imperceptible. Other techniques analyze the energy of a far-end call signal. However, such techniques cannot typically distinguish a live human voice from a pre-recorded voice, as is often generated by an answering machine; interactive voice response ("IVR") unit, or the like.
Accordingly, an improved technique that may be used in assessing call progress in a call establishment system, and that may estimate the source of a far-end voice signal that may originate with a live human or a machine is desirable.